Understanding Your Home's Foundation

A slab foundation is made of concrete that’s typically 4 to 8 inches thick. Concrete slab foundations are more common in states with warm climates, where the ground is less likely to freeze and cause the foundation to crack. Contractors pour concrete footings about 2 feet into the ground and add a layer of sand, gravel or rock to help with drainage. Steel rods, or rebar, are often added to the slab for reinforcement to support the home’s weight.

Slab foundations are less prone to flooding than other foundation types. The design guides rainwater drainage away from your home. There’s less chance for developing mold and mildew with a slab than with crawlspaces and basements. Homes on a slab also cost less to construct.

Some disadvantages include that heating and cooling units may have to be installed on the ground floor, and water and sewer lines are embedded in the concrete. There’s also a potential for cracks if the soil becomes unstable.

A home built with a crawlspace has an elevated wall foundation with support footings raised 18 inches to 4 feet above the ground. The short height only allows for stooping or crawling in the space, thus the name. This open space provides a buffer from the cold ground or concrete slab, allowing warm air to circulate under the home’s floors. A home with a crawlspace can allow for access to plumbing, duct work, and heating and cooling units.

A crawlspace is ideal for homes that sit on sloped lots where a slab can’t be used or a basement is too costly. A crawlspace is about double the expense of a concrete slab but still costs less than a full basement. Maintenance is also required with a crawlspace to avoid excess moisture buildup that can possibly lead to mold and mildew. Waterproofing with a vapor barrier can help prevent moisture buildup and improve home air quality. Vented crawlspaces are also susceptible to insects and other pests.

A basement is the deepest of the three foundations. There are two types of basements: full basements and walk-out or daylight basements. Full basements have concrete or concrete block walls, which are generally about 7 feet high and usually match up with most or all the flooring area directly above. You enter a full basement from the floor above via a staircase. Walk-out or daylight basements are found on homes built on a slope and have one or more of the basement walls set against the terrain. The other open walls provide options for windows to bring in natural light or a rear entrance to the backyard. Both types of basements can provide extra storage and additional living areas like a game room, recreational area or spare bedroom. However, basements add significant additional costs to a home’s construction, and there may be moisture and humidity issues if you don’t follow proper steps to address them. Full basements are more prone to these problems than daylight basements.